Telegraph transmitter



Sept- 19, 1939.V w. .1. zENNER TELEGRAPH TRANSMITTER Filed Sept. 25, 1936 3 Sheets-Sheet 1 FIG.

INVENTOR WALTER J. ZENNER BVM ATToRN sept. 19, 1939.

W. J. ZENNER TELEGRAPH TRANSMITTER Filed Sept. 25, 1936 3 Sheets-Shea?I 2 yFIG. 3

Dn E N9 N RE OZ T l NJ E VR NE u A W ATTOR N EY FIG. lo '|9.

Sept. 19, 1939. w. J. zENNER TELEGRAPH TRANSMITTER Filed Sept. 25, 1936 3 Sheets-Sheet 3 INVENTOR WALTER J. zENNER ATTORNE Patented Sept. 19, 1939 UNTED STATES PATENT OFFICE TELEGRAPH TRANSMITTER tion of Delaware Application September 25, 1936, Serial No. 102,443

18 Claims.

The present invention relates to printing telegraph apparatus and is concerned more particularly with keyboard control mechanism adapted to isochronous signal transmission.

The principal object of the present invention is to provide a transmitter mechanism which is simple and inexpensive in its construction and efficient and positive in its operation and which is adapted to monopulse isochronous signals each having a selecting interval and an accompanying interval which constitutes the periodic remainder or complement of said selecting interval.

In its preferred embodiment, the present invention contemplates a transmitter mechanism that is especially adapted to the propagation of monopulse isochronous code signals to be used in operating telegraph printers of the class particularly described and illustrated in copending application, Serial No. 49,663, led November 14, 1935. A characteristic ofthe contemplated systern of transmission is its use of synchronized transmitter and receiver shafts having cyclic rotation and being normally stopped in a Zero position. When released by the depression of a keylever which alters the polarity of the line, a selecting impulse is initiated which has a variable duration, and in accordance with its extent is individually significant of a character selection. The point of termination of the selective impulse constitutes the determining factor by which each selection differs from the general class. Since the over-all period is coincident with a complete cycle of rotation, the instants at which the selective impulse is determined are controlled by a corresponding number of manual key bars arranged in a circular or arcuate distribution. Appropriate latching means are provided whereby in response to the depression of each key bar, the remaining ones are locked against operation pending the termination of the particular cycle. Also, safeguard means is provided for preventing through inadvertent operation, the continuous depression manually of each keylever from causing repeated signals to be inaugurated and requiring instead, that each key bar be permitted to return to its normal position before it or any other key bar may be actuated subsequently. Means are also provided for excepting from the repeat signal precautionary safeguard certain kelevers of which the space key bar has been herewith solely included, but which might embrace other key bars whose performance is desired to be thus qualified.

In perfecting the present invention, certain features have been developed, noteworthy among which are the staggered arrangement of key bars in an arcuate distribution so that the control portion of each bar is presentable in the path of arevolving trip element carried by a centrally located transmitter shaft, the provision of a circular locking disc which is rocked upon the depression of each key bar and thereby is displaced so as to block the operation of the remaining key bars, and the provision of double stop mechanism for arrestingV the distributor shaft cyclically at its zero position, notwithstanding the continuous depression of any keybar.

For a more comprehensive understanding of the aforo-enumerated features and of the manner in which the described objects are achieved, reference should be had to the accompanying drawings and to the following detailed specification wherein like reference characters indicate corresponding parts throughout and wherein,

Fig. l is a plan View of a transmitting and printing unit having a circular transmitting keyboard designed in accordance with the features of the present invention; 25

Fig. 2 is a longitudinal sectional View through the apparatus featured in Fig. 1 and istaken approximately on line 2 2 indicated thereon;

Fig. 3 is a transverse sectional View through the unit featured in Fig. l and is taken approxi- 30 mately on line 3-3 indicated thereon;

` Fig. 4 is a plan sectional detail View of the keyboard mechanism and is taken approximately on line 4 4 of Fig. 2;

Fig. 5 is a view similar to Fig. 4, having por- 35 tions broken away and featuring an alternative condition of operation;

Fig. 6 is a fragmentary detail View of theyrevolving seeker assembly carried by the distributor shaft; 40

Fig. 'l is a view similar to Fig. 6 featuringan alternative condition of operation;

Figs. 8 and 9 are fragmentary detail views of a modified form of double stop mechanism which may be substituted for the one featured in Figs. 4 and 5;

Figs. 10 and 11 are fragmentary detail views of the key bar extremities showing their normal and actuated positions and the manner in which they affect the key bar locking disc;

Fig. 12 is a diagrammatic chart portraying a typical selecting signal (for the alphabetical character K) such as is used in the control of apparatus to which the present invention is particularly adapted;

Fig. 13 is a detail perspective View of one of the key bars; and

Fig. 14 is a sectional detail view taken approximately on line Ill-I4 of Fig. '1.

Referring now more particularly to the accompanying drawings, the reference character I I will be observed to indicate a base plate around which there is fitted a housing I2. The fore portion of housing I2 is conformed into a circular sleeve or annulus I3 which juts from the housing I2 at a slight angle and into which there is tted the keyboard assembly I4. The principal support of the keyboard assembly I4 is obtained from a circular bottom plate I5 in which there are made a plurality of radial slots I6, Fig. 5. Directly above the bottom plate I5 is a supporting ring I1 having radial slots I8 which correspond, each to each, with the slots I6 of plate I5. Traversing each pair of slots I6 and I8 and slidable therein is a key bar I9, Fig. 13, having a key top 2l individually designated by a character or numerical legend, as may be noted in Fig. 1. In order to render the several key bars I9 and their key tops 2l sufficiently compact to be assembled within a small radial group, alternate bars I9 are similarly designed with their key tops extending towards, and the intermediate ones away from, the center of the assembly circle.

Each key bar I9 is provided with a pair of stop shoulders 22 which encounter the surfaces of the supporting ring I1 to limit the movement of the bar in each direction and a downwardly extending portion divided into two sections 24 and 25 by a notch 23. The section indicated 24 is preferably the narrower and about it is coiled an individual return spring 26 whose ends abut the top surface of the floor or base plate I5 and the shoulder lugs 21 especially provided for this purpose and integrally formed with each key bar I9. The individual return springs 26 tend to maintain the key bars I9 in their upper position as portrayed in Fig. 2J but upon being depressed, a key bar is capable of movement until its stop shoulder 22 encounters the supporting ring I1. Parallel movement is assured each key bar by its confinement within slots I6 and I8 where it is secured against lateral displacement by the retainer rings 28 and 29, the former being secured to the floor plate I5 and the latter to the supporting ring I1.

A dependingtooth 3| of key bars I9 is inclined at an angle with respect to the body portion thereof, as best indicated in Fig. 13, and preferably is beveled at its extremity 32 so that it may enter between adjacent vanes 33 of the locking disc 35, as shown by the left key bar I9 of Fig. 11, without positively encountering the foremost surface of an oncoming vane, it being noted that by a camming action the under surface 34 of each tooth 3I upon encountering the vane 33 immediately below it causes the locking disc 35 to be rotated clockwise (Figs. 4 and 5) through a limited distance. After each key bar operation, the locking disc 35 is held for a time when its upstanding lug 91, Figs. 4 and 5, is restrained by the latch pawl 99. In moving clockwise, the locking disc 35 opposes the action of a return spring 31 (Figs. l and 4) connecting one of its spokes 38 with an anchor screw 39. When one of the bars I9 has been actuated, causing the locking disc 35 to be rotated clockwise into its key bar locking position, it will be noted that any attempt to depress another key bar I9, such as the right-hand one of Fig. 11, will be futile because its tooth 3| will encounter squarely one of the vanes 33. Moreover, the restraining action of latch pawl 91 staying the return of locking disc 35 also prevents the return of the actuated key bar, notwithstanding the efforts of its individual spring 26, for the inner surface 36, Fig. 11, upon encountering its contiguous vane 33 is unable to move the latter counterclockwise as is its tendency to do during the return motion. Upon the release of pawl 99 as will be later` described, the actuated key bar is freed and is then permitted to respond to its spring 25.

The key bars I9 surround a distributor shaft 4I (Figs. 2 and 5) which is journaled within a sleeve 42 (Fig. 2), securely held to the bottom plate I5 by the lock nut 43 which draws plate I5 between itself and a collar ange 44 formed with sleeve 42. The locking disc 35 is journaled upon sleeve 42 within a space provided between a reduced section of the collar 44 and the double lock nuts 45.

The end of shaft 4I, which protrudes beyond the upper extremity of sleeve 42, has secured to it by means of a lock nut 46, a circulating plate 41, While the opposite end of shaft 4I has secured to it the collars 48 and 49 between which are supported the clutch discs 5I of a friction clutch assembly including the friction washers 52 and the driven worm wheel 53. A driving worm wheel 54 meshes with wheel 53 and is secured to an intermediate shaft 55 which is journaled within the uprights 56 of a supporting bracket 51. The other end of shaft 55 carries a driven gear 58 to which power is communicated by a worm 59 carried upon the rotor shaft 6I of an electric motor 62.

'I'he power supplied by the electric motor 62 is utilized not only to drive the distributor shaft 4I through the gear train just described, but is also used to drive the printer shaft 63 through the frictionally driven worm wheel 64 in a manner which is explained in the above referred to copending application. The printer shaft 53 and transmitter distributor shaft 4I thus are arranged to be operated from a common power source, thereby constituting the assembly a compact and unitary apparatus. The printer apparatus is preferably enclosed in an individual housing or cover 65 whose fore plate 66 partially divides the interior chamber between the transmitter unit and the printer, as best indicated in Fig. 2.

Referring now to Figs. l and 4, it will be noted that when the transmitting distributor shaft 4I is in its zero or normal stop position, as indicated, a depending lug 61 integrally formed with the circulating plate 41 is confronted by a stop arm 68 of a bell crank pivoted at 69 upon a stud screw. The other arm 1I of the bell crank is bifurcated to receive a pin 12 which rises from the locking disc 35. When the locking disc 35 has been rotated clockwise, as illustrated in Fig. 11, following the depression of a key bar I9, it causes through the aforedescribed articulation with bell crank Gil-1I, the movement of the latter clockwise about pivot screw 69, withdrawing arm 68 from the path of the depending lug 61. Thus the actuation of a key bar I9 acting through lock plate 35 and its pin 12 causes the distributor shaft 4I to be freed to respond to the influence of its driven wheel 53.

As the shaft 4I and its circulating plate 41 enter upon a cycle of revolution, the seeker arm 13 which is pivotally supported at 14 upon plate 41, revolves with its extremity 15 passing by each of the key bars i9 until it encounters the particular one of them which has been depressed, whereupon it collides with its sidewardly extending Vane 16, Fig. 13, beneath the lowermost shoulder 22. The normal or starting position of seeker arm 13 is that illustrated in. Fig. 4, at which time it is found in its counterclockwise extremity with respect to pivot 1t, whereat the shoulder 11 of a latching pawl 13 is seated within the foremost notch 19 of. a pair of notches 1S and 85 formed in seeker arm i3. The latching pawl 1B is pivoted upon plate @1 at pivot screw 8i and is urged in a clockwise direction by a spring 82 which concurrently urges seeker arm 13 in a clockwise direction about its pivot screw 1d, Figs. 6 and 1. When shaft 4i is released for rotation and before the extremity 15 of seeker arm 13 has had an opportunity to encounter the position of the first key bar I9, which relates in the present embodiment to the special character an outwardly extending web S3 which is integrally formed with latching pawl 18 encounters a trip pin 84 which extends from the supporting ring I1. This causes latching pawl 16 to be rocked counterclockwise in opposition to the iniiuence of its spring 82, withdrawing the shoulder 11 as illustrated in Fig. 6 from the foremost notch 16 and permitting seeker arm 13 to be urged by spring 82 clockwise about its pivot Eli or until the shoulder 11 is received within the rearmost notch 85. As a result of this, the extremity 15 of seeker arm i3 is moved outwardly from the pivotal center 4i, a short distance which is sui-ficient to present it into the path of the blade or vane 16, Fig. 14, of any particular key bar i9 which has been depressed. The collision of extremity 15 of seeker arm 13 with the actuated key bar i9 causes arm 13 to be rotated counterclockwise, returning it to its original position as illustrated in Fig. '7, at which time latching pawl 18 again falls into the foremost notch 19 where it continues throughout the remaining portion of a cycle.

It will be observed that upon the actuation of any key bar IS or li l a short angular movement Will be consummated (corresponding to the angular distance between web 352 and trip pin S4) beforethe contact pair is opened Thereafter the effective character signal, which may be considered as the time between the contact opening instant and the instant at which seeker extension 15 encounters a vane 16, is of measured length. To permit of some adjustment in regulating the length of the effective character signal, it is proposed that trip pin B4 be made movable with any conventional means for securement.

The seeker arm 13 controls a pair of contacts 86-81, normally maintaining them closed and causing a continuous current condition to flow which, in accordance with the particular embodiment, is the normal line condition. At the instant when latching pawl 18 is tripped by trip pin 84 and seeker arm 13 is permitted to assume its released or seeking condition, the aforementioned Contact pair 86-81 is open and continues to remain so until the extremity 15 collides with the portion 1B of a depressed key bar I9; thus, the character selecting interval may be noted as one corresponding to the angular distance between the xed point at which latching pawl 18 is released by pin 84 and the variable point at which extremity 'l5 encounters the portion 16 of a depressed key bar 19.

The manner in which seeker-arm 13 controls the contact pair 86-81 is indicated best in Figs. 2 and 4 where it will be noted that a bell crank lever 63 is pivoted at 39 to an upstanding lug 9i integrally formed with circulating plate 41. The horizontal arm of bell crank lever 88 rests against an insulation block carried by the contact blade 81 urging it into contactual engagement with its associated blade 86. The downwardly extending arm of bell crank lever 38 is received in the forked end 92 of a branch arm 93 of seeker arm 13. When the seeker arm 13 is in its normal or stop position, in which it is illustrated in Fig. 4, a bell crank lever 38 is maintained in its counterclockwise extremity, Fig. 2, holding the' contact pair 86-81 together, but when released into the position indicated in Fig. 6, the forked end 92 of lever 13 causes bell crank lever 88 to be rotated clockwise as viewed in Fig. 2, so that its horizontal arm recedes from the contact blade 81, permitting the contactors to open.

As has already been said, the time interval when the contact pair 86-81 remains open may be aptly referred to as the selecting impulse during which, in accordance with the preferred embodiment, no current is supplied to the line. This interval is determined at the point indicated @fl in Fig. 5, where one of the key bars is depressed, presenting its blade 16 into the path of seeker arm extremity 15 (see also Fig. 7). Thereafter the contact pair 86-81 is again closed, continuing in this condition not only to the conclusion of the particular cycle but thereafter until broken again as a result of and following shortly the actuation of another key bar i9. In Fig. l2, there has been portrayed diagrammatically a signal condition corresponding to the alphabetical character K and the signal impulse represented by the bracketed reference character 95. The remaining portion of the cycle is indicated by the bracketed reference character 96, and may lbe termed the complementary portion or the complement of the signal impulse, it being obvious that the signal portions 95 and S6 combinedly comprise a constant time unit which corresponds with a complete revolution of the distributor shaft 4I.

Vvhen the locking disc 35 is rotated clockwise by the actuation of one of the key bars I9, Fig. 5, the latch lug 91 integrally formed therewith is moved to the left sufciently to fall behind the tooth 98 of a latch pawl 99 which is pivotally supported at 10i upon a shoulder screw and is provided with a curved release arm |02, the extremity of which extends into the path of the depending lug 61 as it nears the final few degrees of its rotation. Latch pawl 99 is influenced by a spring 63 in a clockwise direction so that lock plate 35 is held latched in its actuated or extreme clockwise position until. latch pawl 99 is released by lug 61 at the conclusion of a cycle, at which time the return spring 31 causes locking disc 35 to be rotated counterclockwise until it encounters its eccentrically'adjustable stop 4U. As this occurs, the actuated key bar i9 is restored by its individual spring 28.

Calling to attention again the release operation when stop arm 68 was withdrawn from the path of the depending lug 61, it is noted that a secondary stop lever 104, Fig. 5, is pivoted at M35 upon a pivot stud which extends from the bottom plate l5. One arm H36 of lever 6&4 terminates with a, sidewardly extending stop lug which is presented directly above the extremity of stop arm S8. The other arm of lever lllli has connected to it a spring |01 and at its extremity terminates with a sidewardly and upwardly extending projection |00, see also Fig. 2, which is beveled to cooperate with the correspondingly beveled surface formed in a projecting portion |09 of the space bar III. Under normal conditions, the secondary stop lever |04 is maintained in its counterclockwise extremity (Fig. 4) opposing the action of spring |01, because the springurged arm is withheld by a stop pin I I2 which is carried by the locking disc 35. Upon the rotation of locking disc 35 in a clockwise direction, pin ||2 is withdrawn, permitting secondary stop lever |04 to be rotated clockwise until the lug extremity of arm |06 extends into the path of depending lug 51. Initially this movement is barred by the obstruction of lug Bl itself, as indicated in Fig. 5, but as the latter passes over this region, the lug extremity of arm |06 is permitted to come fully into the path of lug 61, so that towards the conclusion of its cycle of rotation, circulating plate 41 is arrested when its depending lug 61 collides with sidewardly extending lug |06. This condition will not obtain, except When a key bar I9 is held depressed, for otherwise, the aforedescribed return movement of locking disc 35 would, through stopy pin II2, withdraw secondary stop lever |04. Thus there is prevented the repetition of character signals in response to a single key bar actuation, making it necessary to depress a given key bar repeatedly in order to obtain repeat characters intentionally.

It has been deemed preferable that the no-repeat feature just described be rendered ineffective in the case of tape feed or space signals which are issued by the depression of the space bar I I I.

For this purpose, the space bar III has been provided with the already mentioned projecting portion I 09 which, as the bar I II is depressed,

engages the sidewardly and upwardly extending projection I 08 for holding secondary stop lever I 04 counterclockwise against the influence of spring |07 while the space bar III is in its depressed condition. This practice permits of the sending of a series of consecutive space signals as for the purpose of feeding out lengths of tape, etc.

It will be observed that the space key bar III differs in one respect from the uniform contour of the general class of key bars I9 insofar as the former is not provided with a vane or blade 'I6 to be encountered by the seeker arm extremity 15. As a result, it would appear that when seeker arm 73 is released, following the depression of the space key bar III, and because latch pawl 'I8 is tripped by pin 04, the resulting opening of the contact pair 86-0'1 is not restorable as in the case of any other key bar. This is not the case, however, for there is provided a rigid spur (Fig. 4) which is secured to the frame and which extends into the path of lever end I5 when lever 'I3 is in its released or tripped condition. Thus, in the case of space key bar operation and if for any other reason lever 'I3 is not restored by one of the general class of key bars I9 during its cycle of revolution, spur I I5, being presented after the circular arrangement of key bars, serves to reset seeker lever 'I3 and accordingly to close the contact pair 86-07 assuring that current condition is restored to the line, a fundamental prerequisite to proper line supervision.

In Figs. 8 and 9, there is illustrated a modified construction of the double stop feature which may be substituted for the stop bell crank IEB-1| and the secondary stop lever |04. In this embodiment, an inert supporting plate has been indicated 20|,

upon which there is mounted a pivot block 202. The primary stop element in the case is also a bell crank lever having a depending arm 203 and a sidewardly extending arm 204. Bell crank lever 203-204 is pivoted at 205 in the block 202, while above it at 205, is pivoted a secondary stop in the form of an arm 201. The depending arm 203 of the primary stop terminates With a pin 208 which extends through a hole in the locking disc 209 which is the counterpart of disc 35. The normal position of disc 209 is illustrated in Fig. 8 and its actuated position in Fig. 9. While moving from its normal to its actuated position, the secondary stop arm 207 is urged to trail arm 204 by spring 2|I. Noting Fig. 8, it will be observed that the extremity of arm 20'! is beveled as at 2|2. During transit, therefore, when an extending lug 2I3, which is carried by a collector plate and which corresponds to the aforedescribed lug 61, is freed by the receding of portion 2M of arm 204, then arm 201 is withheld from following arm 204 due to the interference of lug 2|3. After completing its cycle of rotation, lug 2I3 again approaches the vicinity and then nds arm 201 in the position indicated in Fig. 9, whereupon it collides squarely with it and prevents the repeated transmission of character signals in response to a prolonged manual actuation of a key bar.

While the present invention has been illustrated and described in contemplation of a specilc embodiment, it will be understood that numerous variations and modifications may be made without departing from the spirit of the present invention. It is, therefore, intended not to be limited by the details of the foregoing specification nor by the illustrations of the accompanying drawings but to be permitted instead a latitude of interpretation, as indicated by the hereinafter appended claims.

What is claimed is:

l.. In a transmitting mechanism, a rotatable member carrying a portion movable also longitudinally along the axis of rotation into alternative positions7 a switch opened and closed by the longitudinal movement of said portion, power means for imparting rotation to said member frictionally, stop means for arresting said member in a zero position, and a plurality of release means individually actuable for initiating said member into rotation and thereafter for shifting said portion for altering the condition of said switch, said plurality of release means being arranged in a circle about said member.

2. A keyboard transmitter comprising the combination of a circular arrangement of actuators each having a release portion and a trip portion, a revolving member carrying a shiftable arm, a line switch controlled in accordance with alternative positions of said shiftable arm, power means frictionally driving said revolving member, a stop normally presented to arrest the rotation of said member in a zero position, a plate responsive to said release portion of each of said actuators for withdrawing said stop from the path of said revolving member, trip means for shifting said arm as said member is initiated into rotation causing said switch thereby to be opened, and means including the trip portion of an operated one of said actuators for returning said shiftable arm and for closing said switch.

3. A transmitter comprising a line switch, a rotatable switch controlling unit having a seeker arm shiftable between switch opening and switch closing positions, power means frictionally urging said unit into rotation, stop means for arresting said unit in a Zero position, and a plurality of actuators each having stop release means and a projection for engaging said shiftable seeker arm during the rotation of said unit.

4. A transmitter for issuing monopulse signals varying in characteristic in accordance with the duration of their signal intervals, comprising a start-stop rotatable member carrying means for controlling a line switch, a plurality of key bars, means under the control of each of said key bars for releasing said member for rotation, means to cause the opening of said line switch upon the release of said member, and means individual to each of said key bars for engaging said switch controlling means during the course of travel of said member to determine the duration of a signal interval.

5. A signal transmitter comprising a switch for interrupting the flow of current in a signaling line, an itinerant switch controlling member having measured cycles of operation, means under the control of said itinerant member upon its initiation into a cycle of operation for opening said switch, and a plurality of means disposed contiguous to the course of travel of said member and individually conditionable to affect said itinerant member for causing it to close said switch at a predetermined point in its travel.

6. In a keyboard transmitter, a circular arrangement of key bars each having a bent portion, and a shiftable locking disc having a plurality of vanes each cooperating with the bent portion of an associated one of said key bars, said vanes being deflected and spaced from each other to receive therebetween the bent portion of a rst actuated key bar and upon being shifted to abut per-pendicularly the bent portion of any other key bar.

7. The combination set forth in claim 6 including latch means for holding said disc in its locked position, a signaling circuit controlling member having cyclic rotation, and means for releasing said disc.

8. In a telegraph unit, means for transmitting isochronous control signals comprising a revolvable switch controlling member, start-stop means for controlling the revolution of said member, a trip for releasing said member to initiate each cycle of revolution, and a plurality of actuators arranged successively contiguous to the course of its travel to be manipulated for engaging said member and for thereby determining its switch controlling characteristics.

9. A telegraph transmitter having a` rotatable assembly, a switch controlling member included in said assembly, a plurality of actuators arranged in a circle each having means for releasing said assembly for rotation from a Zero position, a trip member for conditioning said switch controlling member, and an abutment member carried by each of said actuators and effective upon the actuation of one of them to engage said switch controlling member to return it to its normal position.

l0. A device for issuing telegraph signals comprising a circuit breaker in a line circuit, means including a shiftable member spring urged into circuit breaker opening position, a latch for maintaining said member in circuit breaker closing position, start-stop arresting means, a plurality of manipulation elements, a carrier for said latch and said shiitable member friotionally urged into motion but controlled 'by said start-stop means under the actuation of one of said manipulation elements to move in cycles and to release said latch at the start of each cycle, and means associated with each of said manipulation elements for restoring said shiftable member and setting its said latch as said carrier traverses the proximity of an actuated one of them.

11. A transmitter comprising a plurality of depressible key bars arranged circumferentially about an axial center, a disc pivoted at said center having a plurality of vanes each associated with one of said key bars, means carried by each key bar for engaging its associated vane and for thereby displacing said disc to present the other of said varies so as to prevent the actuation of any of the other of said key bars pending the return of a depressed key bar, a start-stop controlled shaft, and means carried by said shaft for releasing the depressed key bar and for thereby permitting the restoration of said disc.

l2. A transmitter comprising, a start-stop shaft, a source of power, yieldable means tending to rotate said shaft continuously under impetus of said source of power, a plurality of key bars arranged circumferentially about said shaft, means under the control of each of said key bars for releasing said shaft for rotation, and stop means for arresting said shaft invariably in the Zero position following each operation of said key bars.

13. A keyboard transmitter comprising a line switch operable togenerate start-stop signals consisting of two different current conditions the sum of which is always of constant length, a switch controlling mechanism frictionally driven by a continuous power source, a plurality of manipulators, means for arresting said switch controlling mechanism in a zero position so as to maintain said switch in line normalizing condition, means associated with each of said manipulators for instantly withdrawing said arresting means to permit said mechanism to enter upon a cycle of rotation under impetus of said power source and to alter the condition of said switch, and means individual to each of said manipulators and operable after the lapse of a predetermined time interval peculiar to each of said manipulators for reestablishing to said mechanism its normalizing control condition over said switch.

14. In a keyboard transmitter, a plurality of manipulators, a line switch, an itinerant seeker mechanism capable of assuming seeking and nonseeking conditions, means for moving said seeker mechanism into successive positions for regarding each of said manipulators sequentially, a member controlled by any of said manipulators for releasing said seeker mechanism to its moving means in seeking condition, and means associated with each of said manipulators for restoring said seeker mechanism to non-seeking condition.

l5. 1n a switch controlling apparatus, a frictionally driven shaft, a stationary switch, a switch controller carried by said shaft, means for holding said shaft in a zero position, a plurality of releasers, and means under the control of any of said releasers for withdrawing said holding means and for conditioning said switch controller.

16. A transmitter for issuing isochronous signals comprising a line switch, a switch controller, manual control means for conditioning said switch controller to cause said switch to assume one condition for a given time interval and automatically effective means for causing said switch controller to alter said switch into another condition for a complementary time interval.

17, In a transmitting mechanism, a rotatable member, a portion carried by said member and movable also longitudinally of the axis of rotation of said member into alternative positions, a switch opened and closed by the longitudinal movement of said portion, frictional driving means for rotating said member, a stop for arrest ing said member in a zero position, a plurality of release elements individually actuable, a common device conditioned by said release elements for initiating said rotatable member into rotation, and means associated with each of said release means for shifting said portion, said plurality of release means being arranged in a circle about said rotatable member.

18, In a printing telegraph system, a sending device for generating isochronous signals of two different line conditions including means for producing a normal line current, means for altering said normal line current at an instant in a cycle corresponding predeterminedly to a signal characteristic, and means for restoring said normal line current so that the total line time of normal and altered line current condition is equal for all characters transmitted.

WALTER J. ZENNER. 

